问题
选择题
Dad, I volunteer my time the trees.[ ]
A. to plant
B. planting
C. planted
D. be planted
答案
答案:A
Dad, I volunteer my time the trees.[ ]
A. to plant
B. planting
C. planted
D. be planted
答案:A
短周期元素A、B、C的位置如图所示,已知B、C两元素所在族序数之和是A元素所在族序数的二倍,B、C两元素的原子序数之和是A元素的4倍,则A、B、C依次是( )
A | ||
B | C |
C.O、P、Cl D.B、Mg、Si